1. Field of the Invention
This invention relates to an oscillator, more particularly to a temperature-controlled type oscillator.
2. Description of the Related Art
Crystal oscillators are applied as a reference frequency source not only in wireless communications systems, but also in mobile phones, personal digital assistants (PDA), and notebook computers. A crystal oscillator can be of the well-known quartz crystal oscillator. The resonant frequency of the quartz crystal oscillator, however, varies with temperature. To solve this problem, it has been proposed to use temperature-controlled type oscillators, such as an oven-controlled crystal oscillator (OCXO) or a temperature-compensated crystal oscillator (TCXO).
FIG. 1 illustrates a conventional OCXO 9 that includes a package module 91, a circuit module 92, and a plurality of conductive pins 94. The package module 91 includes a metallic cover 911, and a metallic base 912 that is attached to the metallic cover 911, and that cooperates with the metallic cover 911 to define an airtight space 90 therebetween. The circuit module 92 is disposed in the airtight space 90 in the package module 91, and includes a dielectric substrate 921, a heating controller circuit 923, and a crystal resonator 922. The dielectric substrate 921 is attached to the metallic cover 911 of the package module 91 and has opposite first and second surfaces. The heating controller circuit 923 is mounted on the first surface of the dielectric substrate 921, and is operable so as to generate heat in order to maintain the airtight space 90 in the package module 91 at an operating temperature. The crystal resonator 922 is mounted on the second surface of the dielectric substrate 921 and is operable at a resonant frequency. Each of the conductive pins 94 extends into the airtight space 90 through the metallic base 912 of the package module 91, and is connected to the dielectric substrate 921 and the crystal resonator 922 of the circuit module 92. The airtight space 90 in the package module 91 is filled with a foam material 97 to thereby reduce radiation of the heat generated by the heating controller circuit 923 of the circuit module 92 through the package module 91.
The aforementioned conventional OCXO 9 is disadvantageous in that, since the heat generated by the heating controller circuit 923 of the circuit module 92 is nevertheless radiated out of the package module 91 through the conductive pins 94, which therefore requires frequent operation of the heating controller circuit 923 of the circuit module 92, the conventional OCXO 9 consumes a large power.